Meat quality in suckling lambs: effect of pre-slaughter handling

Thirty-three suckling lambs of the Manchega breed were used to compare the effects of pre-slaughter handling (PSH) on initial meat quality and at 7 days post-mortem. Lambs were distributed into three groups: electrically stunned (ESL; n=15), stunned using CO(2) (GSL; n=10) and slaughtered without previous stunning (USL; n=8). Meat quality was evaluated by examining pH, colour (L*, a*, b* values), water holding capacity (WHC), cooking loss (CL), shear force (SF) and drip loss (DL). At 24 h post-mortem, the highest pH corresponded to the USL group (P<0.05) whereas the lowest pH decline (pH(0)-pH(24)) corresponded to the GSL group (P<0.05). Differences in pH among groups disappeared after 7 days post-mortem. In general, PSH did not affect values of WHC, CL and colour parameters. After 7 days post-mortem, there were significant differences between groups in DL, this being lowest (P<0.05) in stunned animals. GSL resulted in more tender meat (lower SF value) than ESL and USL (P<0.05). Moreover, there was no blood splash in any of the carcasses of the GSL group.     

Predicting tenderness of fresh ovine semimembranosus using Raman spectroscopy

A hand held Raman probe was used to predict shear force (SF) of fresh lamb m. semimembranosus (topside). Eighty muscles were measured at 1 day PM and after a further 4 days ageing (5 days PM). At 1 day PM sarcomere length (SL) and particle size (PS) were measured and at 5 days PM, SF, PS, cooking loss (CL) and pH were also measured. SF values were regressed against Raman spectra using partial least squares regression and against traditional predictors (e.g. SL) using linear regression. The best prediction of SF used spectra at 1 day PM which gave a root mean square error of prediction (RMSEP) of 11.5 N (Null = 13.2) and the squared correlation between observed and cross validated predicted values (R²_cv) was 0.27. Prediction of SF based on the traditional predictors had smaller R² values than using Raman spectra justifying further study on Raman spectroscopy.     

Effect of pelvic suspension and cooking temperature on the tenderness of electrically stimulated and aged beef, assessed with shear and compression tests

Electrically stimulated carcass sides of young bulls were suspended at 1 hr post mortem from the aitch bone (pelvic suspension; PS) and Achilles tendon (AT), respectively. After an ageing period of 14 days at 3 °C, shear force (SF) and compression (20 and 80% compression) tests of the Mm. longissimus lumborum et thoracis (LO) and semimembranosus (SM) were conducted in raw muscle and after heating for 1 hr at 55, 60, 65, 70 and 80 °C. Collagen content was higher in SM than in LO, while sarcomere length (SL) of raw muscle were 1.75 and 1.78, for LO and SM. In comparison with the AT-side, PS increased SL by 21 and 47% and cooking loss (at 80 °C) by 2 and 6% for LO and SM, respectively. Drip loss of whole muscles from the PS-side during the ageing period tended to be lower (n.s.). Over the whole cooking temperature range, SF-values were relatively high for the SM in comparison with LO. For both muscles from the AT-side, the lowest SF-values were observed at 60 and 65 °C. The PS-treatment resulted in higher SF- values for raw muscle and after cooking at low temperatures (55 and 60 °C), particularly in the SM. In the intermediate temperature range (65 and 70 °C), PS had no significant effect, while in the higher temperature range (80 °C), SF-values were lower in the PS-side. Similar tendencies were observed in the LO, although the lower SF-values for the PS-side were observed already at 60 °C. In non-destructive compression (20%), there was a gradual increase in stress values with increasing cooking temperature. In comparison with the AT-side, the PS treatment resulted in the LO in similar or higher, and in the SM in lower stress values. With destructive compression (80%), PS resulted in SM in higher stress values in raw muscle and at 55 °C, in accordance with the SF-values. It is suggested that the higher SF- and 80% compression values in raw muscle and at low cooking temperatures, are caused by an increase in collagen strength due to a change in the direction and spatial organisation of the collagen fibres as a result of stretching of the muscle. This study demonstrates that the relative contributions of the collagen and myofibrillar components to the mechanical assessed toughness, as well as the effect of pelvic suspension, is dependent of muscle, cooking temperature and the mechanical test applied.     

Measuring the effects of phenotype and mechanical restraint on proteolytic degradation and rigor shortening in callipyge lamb longissimus dorsi muscle during extended aging

The purpose of this study was to determine if tenderness of callipyge (CLPG) longissimus dorsi muscle (LM) could be improved by: (1) extending the aging period to 48 days postmortem or (2) preventing rigor shortening by clamping. In CLPG and normal (NML) chops respectively, initial Warner-Bratzler shear values (WBS) were lower (P<0.05) in clamped (CL) (5.5 and 3.6 kg) compared to unclamped (UCL) (7.4 and 4.9 kg) LM. In CLPG, an acceptable WBS (3.6 kg) was reached at 48 days PM, whereas, NML lambs reached an acceptable level (3.8 kg) by 3 days PM. Sarcomere lengths (SL) of CL (1.68 μm) were longer (P <0.05) than for UCL (1.44 μm) and were negatively correlated with WBS (r=-0.55; P<0.1). The appearance of Troponin-T (TNT) degradation product coincided with tender WBS values; 3 days postmortem in NML UCL and 48 days postmortem in CLPG. In conclusion, clamping reduced WBS possibly by reducing rigor shortening. Extended aging resulted in CLPG LM with acceptable WBS values, concurrent with the appearance of TNT degradation products.     

牛肉排酸成熟过程中的品质变化

为探究排酸成熟过程中肉类品质的变化,以牛肉为研究对象,测定排酸1～7 d肉样的硬度、保水性、pH值、肌原纤维小片化指数（myofibril fragmentation index,MFI）、菌落总数、大肠菌群数以及排酸1、3、5d时肌原纤维的超微结构。结果表明：牛肉排酸3 d时出现最大僵直期,硬度达到最高,保水性达到最低,pH值降到最低值5.56;随着解僵及成熟的进行,牛肉嫩度、保水性回升,排酸7 d时pH值回升到5.84,达到排酸成熟肉标准（5.8～6.2）;排酸1 d时,肌原纤维的Z线、粗细丝清晰可见,随着肌原纤维小片化程度的不断加深,排酸5d时,Z线变得模糊,几乎消失,成为晕染状,几何构型发生明显变化。上述结果表明,牛肉在0～4 ℃条件下排酸成熟需要7d,前3 d是排酸的关键时期。     

Effect of low-voltage electrical stimulation after dressing on color stability and water holding capacity of bovine longissimus muscle

The effect of low voltage electrical stimulation after dressing (ES) on color stability and water holding capacity (WHC) of beef was investigated. Nine Swedish red cattle were slaughtered and the left side was electrically stimulated (80 V, 35 s) approximately 30 min after stunning, whereas the other side was not treated and used as control. Color and its stability, WHC, and protein solubility were evaluated on longissimus lumborum muscles from the two sides. ES produced a brighter red color at 24h mainly by increasing the oxygenation capacity of myoglobin (P<0.01), which was attenuated by postmortem aging. ES did not affect WHC, protein solubility and color stability (P>0.05). Therefore, this technology could accelerate meat tenderization without any negative effect on commercial attributes, such as color or drip of bovine longissimus muscle.     

Raman spectroscopy compared against traditional predictors of shear force in lamb m. longissimus lumborum

A Raman spectroscopic hand held device was used to predict shear force (SF) of 80 fresh lamb m. longissimus lumborum (LL) at 1 and 5 days post mortem (PM). Traditional predictors of SF including sarcomere length (SL), particle size (PS), cooking loss (CL), percentage myofibrillar breaks and pH were also measured. SF values were regressed against Raman spectra using partial least squares regression and against the traditional predictors using linear regression. The best prediction of shear force values used spectra at 1 day PM to predict shear force at 1 day which gave a root mean square error of prediction (RMSEP) of 13.6 (Null = 14.0) and the R² between observed and cross validated predicted values was 0.06 (R²_cv). Overall, for fresh LL, the predictability SF, by either the Raman hand held probe or traditional predictors was low.     

饲养方式对新疆多浪羊肉品质的影响

分别以戈壁滩放养及工厂集约化饲养的6 月龄多浪羊背最长肌为对象,分析测定不同饲养条件下羊肉的屠 宰性能、pH值、持水力、嫩度、色泽、抗氧化能力、脂肪酸含量、肌原纤维超微结构等指标。结果表明：工厂集 约化饲养组多浪羊肉的嫩度、成熟7 d的亮度值和脂肪酸总量优于戈壁滩放养组（P＜0.05）,而戈壁滩放养组多浪 羊肉的持水力、抗氧化能力、宰后1 d的红度值及多不饱和脂肪酸含量优于工厂集约化饲养组（P＜0.05）;工厂集 约化饲养组多浪羊肉肌原纤维密度较大、直径小,肌原纤维之间排列紧密;而戈壁滩放养组的多浪羊肉肌原纤维密 度小、直径大,肌原纤维之间空隙较大。两种饲养方式各有优势,在生产中可考虑结合已有的饲养条件加以完善, 以生产出更优质的羊肉。     

Effect of different stunning systems on meat quality of light lamb

The present study was proposed to compare the effect that different types of stunning (TS) had on the quality of refrigerated meat from light lambs of the Spanish Manchega breed at 24 h and 7 days post-mortem. Lambs were electrically stunned (ESL; n = 10), using CO₂ (GSL; n = 10) or slaughtered without previous stunning (USL; n = 10). Measurements on meat quality were carried out by evaluating pH, colour coordinates (L^*, a^*, b^*), water holding capacity (WHC), cooking loss (CL), shear force (SF) and drip loss (DL). At 24 h post-mortem, no significant differences were found in any of the variables studied. However, at 7 days post-mortem, meat quality was affected by the different TS: pH, CL and DL were lower (P < 0.001) in the USL group and GSL obtained the lowest a^* (redness) and b^* (yellowness) values (P < 0.01) than in the other groups. Ageing of meat affected SF in the ESL group (P < 0.01), although there were no significant differences due to treatments at any of the ageing times.     

POSTMORTEM CHANGES IN MYOFIBRILLAR PROTEINS OF GOAT SKELETAL MUSCLES

Postmortem changes at 5C in myofibrillar proteins of longissimus dorsi (LD), biceps femoris (BF), semimembranosus (SM) and semitendinosus (ST) muscles and myofibrillar structure of LD muscle of goat were investigated. Muscle samples were immediately collected after killing, and from carcasses stored at 5C for 3, 6, 9, 12 and 20 days. The sodium dodecyl sulfate‐polyacrylamide gel electrophoresis of myofibrils indicated the appearance of a 30 kDa component, depending on the type of the muscles. A new 55 kDa component appeared in BF and SM muscles during postmortem. Titin I and nebulin also disappeared during storage. The disappearance of titin 1 and nebulin and the appearance of a 30 kDa component were confirmed by Western blot analysis. The Transmission Electron Microscopy studies showed that after 3 days postmortem, Z‐disks stayed unaltered. After 6 days postmortem, a little ultrastructural alteration was observed, and at 12 days postmortem a considerable degradation of Z‐disk ultrastructure was shown. The Z‐disk degradation, which results in the fragmentation of myofibrils and the appearance of 30 kDa components, is the major change observed in goat skeletal muscles during postmortem.     

Effect of pelvic suspension on three major leg muscles in the pig carcass and implications for ham manufacture

Thirty-two female pigs were slaughtered and their left sides suspended conventionally by the Achilles tendon whilst right sides were suspended from the pelvic bone. The first 16 pigs were used to measure suspension effects on the characteristics of three major leg muscles (m. gluteobiceps, m. semimembranosus and m. rectus femoris) and to assess their suitability for ham manufacture. The remaining pigs were used for the production of hams, made from tunnel- boned whole legs injected to a target 10% weight gain, then tumbled and cooked. Compared with conventional hanging, pelvic suspension resulted in significantly (P<0.01) lower weight loss from the sides during chilling (2.8 and 2.5%). There were major changes in the shape of all three muscles, with pelvic suspension producing marked increases in the width of the m. gluteobiceps (24%) and length of the m. semimembranosus (34%), and a small reduction in the length of the m. rectus femoris (2%). It also resulted in the two former muscles having a relatively higher brine retention, lower drip losses after storage and lower instrumental texture values (Volodkevitch shear force). Cooking loss was reduced in the pelvic-suspended m. semimembranosus. Similarly, whole gammon hams made from pelvic-suspended sides had greater injection gains than hams from conventionally-hung sides (13.6 and 12.3%), with lower cooking losses (16.7 and 19.0%). Instrumental texture values (punch and die peak force) made on the individual muscles in 3-mm thick slices were lower for the m. gluteobiceps (5914 and 9085 g) and m. semimembranosus (6163 and 7600 g) as a result of pelvic suspension. There were minor but significant effects on some colour parameters which probably have little commercial impact. The results demonstrate the advantages of pelvic suspension in terms of brine uptake and retention, and hence increased yield, as well as reduced toughness, for at least two of the major leg muscles, m. gluteobiceps and m. semimembranosus, with no disadvantage for the m. rectus femoris. Together, these three muscles constitute about half of the trimmed leg weight.     

EARLY POSTMORTEM SKELETAL ALTERATIONS EFFECT ON SARCOMERE LENGTH, MYOFIBRILLAR FRAGMENTATION, AND MUSCLE TENDERNESS OF BEEF FROM LIGHT-WEIGHT, BRANGUS HEIFERS

Approximately 2 h after exsanguination, two skeletal cuts (TC) were made on randomly selected sides from 13 light-weight, Brangus heifers; companion sides served as untreated controls (C). After a 24-h chill period, four muscles (Longissimus muscle from the IMPS#112A ribeye roll, LT, and from the IMPS#180 strip loin, LL; Biceps femoris, BF; Semitendinosus, ST; and Semimembranosus, SM) were excised from each side, vacuum-packaged, and aged for 7 days. Five 2.54-cm thick steaks were cut from each of the muscles to determine the effectiveness of the TC treatment on sarcomere length (SL), myofibrillar fragmentation index (MFI) and cooked beef tenderness. The LT and LL steaks from TC-carcasses had longer (P < 0.05) sarcomeres, and the TC treatment decreased (P < 0.05) Warner-Bratzler shear (WBS) force values for the LT and LL by 35.8 and 33.2%, respectively. Moreover, SL of the muscles from the round were also increased (P < 0.05) by the TC procedure, but WBS force values were not different (P > 0.05) from C. Muscles from the TC sides had similar (P > 0.05) MFI values to those from control sides. This study demonstrated that the TC procedure, when applied 2 h postmortem, can effectively improve cooked beef tenderness of the Longissimus muscle .     

Tenderness of pork muscles as influenced by chilling rate and altered carcass suspension

Tenderness improvements in porcine muscles (M. longissimus dorsi, LD; M. semimembranosus, SM; M. biceps femoris, BF) were evaluated in a total of 72 carcasses by using combinations of three different chilling rates (fast, delayed fast, slow) and two different suspension methods (Achilles tendon, pelvic bone).

Tenderness was improved by fast chilling in LD, SM and BF by the pelvic suspension as compared to conventional suspension in the Achilles tendon (P < 0·05). The lengthening of the sarcomeres in SM and BF as produced by pelvic suspension exceeded those found in LD, without having proportional additional effect on the tenderness. While the pelvic-induced tenderization did not change significantly by delayed fast chilling, additional tenderization in BF and SM was obtained by combining pelvic suspension with slow chilling. In conventionally suspended sides, tenderness was unaffected by delayed fast chilling—with slow chilling, however, improvements were observed in LD and SM to a similar extent as obtained by the pelvic suspension. In the LD muscle, the tenderizing effect produced by treatments was largest in muscles having pH values 45 min post stunning above 6·1 (P < 0·05).     

Any link between integrin degradation and water-holding capacity in pork?

In order to investigate a possible relationship between integrin degradation and water-holding capacity (WHC), integrin was quantified using western blot, and water mobility and distribution was measured by proton NMR T(2) relaxometry at 24h postmortem in pork (n=30) with a large variation in WHC (drip loss varying from 2.8% to 11.3%). Regression analyses revealed correlation coefficients of r=-0.32 (P=0.08) and r=0.40 (P=0.03) for the correlations between the content of integrin determined by western blot analysis and WHC determined as either drip loss or by NMR, respectively. Water mobility and distribution was also measured in 18 meat samples upon 7 days of aging, which revealed a correlation (r=0.54) between integrin content determined by western blot analysis 24h postmortem and the mobility of the myofibrillar water (T(21) relaxation time) at day 7. In contrast, no correlation could be established between integrin content 24h postmortem and WHC at day 7 determined by NMR as the amount of extramyofibrillar water (T(22) population) (r=-0.01). In conclusion, both visualisation by CLSM and quantification of integrin by western blot analyses of suggested that a strong link between integrin degradation and WHC in pork is questionable, whereas integrin degradation seems to have impact on the succeeding development in the mobility of the myofibrillar water.     

Effects of gas composition in modified atmosphere packaging on the meat quality of Spanish Manchega lamb

The effects of four types of packaging atmosphere, each with a different gas composition (20–80% CO₂), on the meat quality of Spanish Manchega lamb were examined in order to suggest a gas composition for optimal preservation. Meat quality was assessed by pH, colour (L*,a* and b* values), water‐holding capacity (WHC), cooking loss (CL) and shear force (SF). Gas composition affected all parameters except L* and SF. The pH values decreased significantly in samples packed with 80% CO₂ but remained constant in the other groups. The b* values were lower in samples packed without O₂ than in the other groups and increased with time. However, the a* values decreased in all groups with time. Samples packed in low‐CO₂ atmosphere tended to lose more water (ie to have less WHC and show more CL). The SF values decreased with time, and similar values of this parameter were observed for all treatments. © 2001 Society of Chemical Industry     

Growth hormone response to growth hormone releasing hormone in calves that differ in genetic merit for milk yield

Holstein heifer, steer, and bull calves from control (CL) and select (SL) lines of cows that differed by more than 4000 kg of milk during a 305-d lactation (SL > CL) were used to determine growth hormone (GH) response to 5 doses of GH releasing hormone (GHRH) and how this response was affected by gender, period (age), and genetic merit for milk yield. Doses (0, 2.5, 5, 10, and 20 microg/100 kg of BW) of a GHRH analog were assigned randomly to each heifer (4 CL, 4 SL), steer (4 CL, 4 SL), and bull (3 CL, 3 SL) calf and administered on consecutive days at approximately 3, 6, and 10 mo of age (periods; P1, P2, and P3). Jugular blood samples (n = 15) collected between -30 and 240 min relative to GHRH administration were used to quantify area under the GH response curve (AUC) after subtracting mean prechallenge GH concentrations. Estimates of maximum response (Rmax) and sensitivity (ED50) to GHRH were obtained from the hyperbolic dose response curves (AUC vs. dose). Data were analyzed for effects of dose, line, period, gender, and their interactions with period as the repeated effect. Prechallenge GH concentrations were not affected by genetic line, gender, or period. The AUC was not affected by line, but decreased with period and increased with GHRH dose. The Rmax did not differ between lines or among genders, but decreased with period. The ED50 did not differ between lines or among periods, but heifers were more sensitive to GHRH than steers or bulls. Although GH response to GHRH has been identified as a potential indicator of genetic merit, it did not differ between these substantially different genetic lines.     

结冷胶与海藻酸钠对低脂猪肉凝胶改性的影响

海藻酸钠和结冷胶作为脂肪替代品,可改善低脂肉糜类产品的品质。本实验将二者加入低脂猪肉糜中,研究这两种多糖对低脂肉糜产品的蒸煮损失、保水性(WHC)和硬度等方面影响。结果表明,浓度大于0.25%的结冷胶单独作用于肉糜时,凝胶的蒸煮损失、保水性和硬度均显著降低(p<0.05);浓度大于0.5%的海藻酸钠单独作用时,凝胶蒸煮损失和硬度显著降低,保水性显著增加(p<0.05);在复配实验中,海藻酸钠对肉糜凝胶蒸煮损失的降低和保水性的提升起主要作用,而结冷胶在低浓度(0.25%)时可协同海藻酸钠显著降低凝胶蒸煮损失(p<0.05),同时有效调控凝胶硬度。     

Influence of Postmortem Changes in Bovine Muscle on the Water-Holding Capacity of Beef. Postmortem Storage of Muscle at 20°C

Rigor mortis occurs in bovine neck muscles as soon as pH 5.9 and an ATP level of about 1 μMol/g are reached. At 20°C muscle contraction does not occur before the onset of rigor. Postmortem changes in water-holding capacity (WHC) were followed by measuring the cooking loss of unsalted and salted (2% NaCl) muscle homogenates prepared after storage of the intact muscle tissue at 20°C for different periods postmortem. At tissue pH above 5.9 addition of salt causes a strong increase of WHC of muscle homogenates. There is a small decrease of WHC of both unsalted and salted homogenates during the prerigor phase which is apparently caused by the postmortem fall of pH. Rigor mortis does not influence the WHC of unsalted muscle homogenates but causes a strong decrease of WHC of salted homogenates. The reason for this difference is discussed. No more than one-third of the total postmortem decrease of WHC and protein solubility in salted muscle homogenates was attributed to the fall of pH, so at least two-thirds were due to the development of rigor.     

Pelvic suspension improves quality characteristics in M. semimembranosus from Swedish dual purpose young bulls

To study whether pelvic suspension would improve tenderness in comparison with normal hanging from the achilles tendon, carcasses from 34 Swedish red and white young bulls were randomly selected at the slaughter line. The left sides of the carcasses were re-hanged by the pelvic bone before cooling whereas the right sides remained hanging from the achilles tendon. Quality characteristics and length and weight were studied for M. semimembranosus. Tenderness was measured by the Warner-Bratzler shear force method. Purge and cooking loss were determined and sarcomere length was measured. Pelvic suspension considerably affected the shape of M. semimembranosus; the length increased by 38% in comparison with achilles suspension. The elongation of the muscle was parallel with an increase in sarcomere length from 1.6 to 2.9μm. The water-holding capacity was improved because both purge and cooking loss were lower for pelvic suspended carcasses. Tenderness was improved and the coefficient of variation between animals for Warner-Bratzler shear force was reduced from 26% for achilles tendon suspension to 12% for pelvic suspension. Likewise, the within-animal variation for shear force decreased significantly from 13.3% to 10.0%. Therefore, pelvic suspension seems to be a reliable method to reduce texture variability in M. semimembranosus from young bulls.     

Inhibition of the proliferation of myeloma cells by the meat origin strain Enterococcus faecium CH3

Sides of 31 non-stimulated carcasses of young bulls were subjected to the muscle stretching methods Tenderstretch (TS) by pelvic bone suspension or Tendercut (TC) with two skeletal cuts or served as controls by traditional Achilles tendon suspension. The sides were chilled at fast and medium rates, resulting in temperatures of 4-5 and 9°C in the m. longissimus dorsi (LD) at 10 h post mortem. The LDs were examined for sarcomere length, Warner-Bratzler peak shear force and sensory properties after 8 days of ageing at 4°C. At the fast chilling rate, TS and TC increased sarcomere lengths, reduced shear force and improved sensory tenderness of the LDs compared to the controls (P<0.05). At the medium chilling rate, sarcomere lengths increased (P<0.05), but no significant differences were found in shear force or sensory tenderness (P>0.05) of the muscles due to stretching. However, the medium chilling rate was efficient in producing tender LDs without applying muscle stretching methods. TS and TC are feasible alternatives for improving overall tenderness and reducing variation in tenderness of beef LD at cold shortening chilling conditions.